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Climate scientists have warned us of coral bleaching for years. It's here
Posted on 10 June 2016 by John Abraham
Readers may have noticed that it’s been about a month since my last article. In recent weeks I presented guest articles in place of my own pieces. The reason for my absence was due to the adoption I was finalizing in the USA (my second successful adoption!). Anyone who has adopted a child can attest to the time and travel requirements. I intend that this article marks my return to near weekly posting and I thank my readers for their patience.
Coral reefs are important for the health of the ocean biosystem; they support and harbor a high density of diverse organisms. While there are reefs located in many locations around the world, people often think first about the Great Barrier Reef off the Australian coast. It is known for its size and beauty; it brings travelers close to nature.
Scientists have investigated how reefs will fare in a changing world. The changing climate, poor management, pollution, overfishing, careless divers, and other factors may bring real risks to the health of reefs.
Just a few days ago, a world-leading organization released the results of a long-term study on the health of the Great Barrier Reef that may tell us about the health of reefs around the world. The organization ARC Centre of Excellence Coral Reef Studies found that a recent mass bleaching has killed 35% of corals on the northern and central Great Barrier Reef.
The National Oceanic and Atmospheric Administration explains coral bleaching as events that cause the coral to expel algae that live in their tissues. Following the expelling, the corals whiten in color (which is why the term bleaching is used). The coral and the algae live in a symbiotic relationship; the algae provide nutrients for the coral. Without the algae, coral can be more susceptible to disease and death. It’s important to know that the coral can recover from a bleaching, but recovery depends on the extent and duration of the event and the general health of the coral.
This year’s incredible bleaching is not a one-time event. In fact, there have been many significant regional bleaching events and three global events over the past 18 years. In the current event, the extent of bleaching depends on location. The Great Barrier Reef extends over 2000 km. In the northern sector, almost all reefs experienced bleaching. The further south one travels, the less extensive the event because the warming was not as severe.
Map of estimated coral loss on the Great Barrier Reef in June 2016, Australia. Illustration: ARC Centre for Excellence in Coral Reef Studies
I asked coral-reef expert John Bruno about this new study and he provided some excellent insights. He told me that this bleaching event is getting a lot of attention because it is the Great Barrier Reef – an iconic place that is close to pristine. It has also escaped the fate of most of the world’s reefs. But, within the scientific community, this bleaching isn’t a surprise. Dr. Bruno told me:
We’ve been witnessing this sort of event for over 30 years. In fact, the Australians have been warning the rest of the world that if we managed our reefs better, we wouldn’t see so many bleaching events.
A very influential paper published in Science in 2003 hypothesized that mass coral mortality events and subsequent population decline only happen where and when fishes have been over-harvested and pollution has weakened the corals and encouraged seaweed growth.
Dr. Bruno told me that this study generated the paradigm of “managed resilience” in coral reef ecology. The central theme is that better management of fishing and pollution makes reefs more resilient to bleaching and allows reefs to more easily recover if an event occurs. But the foundation of this paradigm has been challenged by the fact that nearly every critical test has shown it ineffective. So, the connections of warming oceans, pollution, management, fishing to bleachings are still being investigated. He further told me:
Beyond demonstrating once again that emissions and ocean warming are causing massive coral loss, this study demonstrates that even remote, well-managed, and barely impacted reefs are susceptible to bleaching and ocean warming. The intact food webs, large predatory fish, and lack of pollution have clearly not made the northern Great Barrier Reef more resistant to ocean warming than reefs near large cities. In fact, this finding is concordant with numerous past studies that have found reefs with higher coral cover (such as reefs in Marine Protected Areas) are more vulnerable to climate change, simply because they tend to be dominated by coral species that are very sensitive to anomalously high ocean temperatures.
What I didn’t realize is that there are also mass bleachings in the Indian Ocean and central Pacific which are getting much less attention.
Nice article but the comment that the Great Barrier Reef is (or was recently) "close to pristine" is completely wrong. At best one might say the northern quarter was relatively pristine (and unfortunately this experienced the worst bleaching) but the southern three quarters was already heavily degraded with more than 50% of the coral lost, dugong populations in severe decline, seagrass in episodic die-offs, and other issues. I can't believe this statement came from John Bruno who published some of the earliest papers showing the state of decline of the coral on the GBR. So I assume it came from elsewhere but should be corrected.
Many Australians are now resisting the establishment of a coal mine in Queensland that will export coal to India as this acivity will add to the problems harming the Great Barrier Reef.
Currently there is anxiety about coral bleaching, affecting particularly the northern Great Barrier Reef. Valerie Taylor had a short informal interview in The Weekend Australian’s Magazine, May 14. You may recall she made many documentaries with her husband Ron about sharks. She’s now 80, and still dives. [Current researchers would/should have been aware of their well known documentaries.] She says of the GBR,
“In 1965 we went from one end of the reef to the other, over six months, and we found bleaching then. In the ‘70s we went back and you’d never know it happened. The coral had recovered; nature had taken care of it. I’ve seen reefs in PNG that were as white as snow and I’ve just come back from there and they’re terrific.”
She thus observes that bleaching is reversible. (Presumably spores from unaffected corals can flow in again to re-colonise affected areas once the cause has departed.)
Coral bleaching and repair occur independently of atmospheric CO2 levels.
As it is mainly the relatively untouched northern areas of the GBR affected, it is unlikely that run-off is the cause. The current bleaching decreases towards the south, flowing on the north-to-south counter-clockwise current from Vanuatu, and becoming depleted in the process. Upstream undersea volcanic activity around Vanuatu produces toxic H2S (Chapter 4a, Cyclone Pam), in time oxidising to sulphuric acid, which may also be a concern; Chapter 5 shows acidity produced by CO2 is not.
Other coral bleaching areas around the globe, eg Seychelles, Caribbean, Maldives, etc are downstream from undersea volcanic areas.
[Rob P] Coral reefs are dying out at the rate of 1-2% per year, and it's very much 'settled science' that the mass coral bleaching and subsequent mortality that we are observing is as a result of sea surface temperatures rising above their normal summertime maximum. See Ove Hoegh-Guldberg's 1999 paper for a detailed rundown.
This why NOAA's Coral Reef Watch program can reliably predict bleaching events some months in advance. The bleaching of the Great Barrier Reef, and elsewhere, was predicted 3-4 months before it happened, and their climate model-based projections anticipate extraordinary bleaching in the Coral Triangle later this year.
You replied as Moderator. Which facts and observations in my post are an issue?
[Incidentally, in my previous post I referred to chapters in my site, “Planet Earth Climate Topics” at pjcarson2015.wordpress.com]
pjcarson2015 @4:
Yes. As always you spammed an add for your site which contains, as usual, a great paucity of facts, a significant number of inventions, and a curious refusal to correct errors. On this topic it contains no information in addition to the text of your post @3 and therefore is not an independent source of evidence, or indeed a source of evidence at all.
As to your post @3, yes coral recovers from bleaching. Recovery, however, takes time. If there are repeated impacts during that time, recovery will be slow, or not occur at all. As can be seen below, events causing damage to reefs have accellerated in recent times, and for the Great Barrier Reef, that has lead to a long term decline in coral cover (second figure):
(Source)
(Source)
As you can see, that decline has been precipitous for the southern most (and most disturbed) portion of the reef.
What is worse, as can be seen from calcification studies, that decline comes at the tail of a reversal of a century long increase in reef health in the mid 20th century (figure d):
Granted that bleaching events currently account for only 10% of reef damage. However, the GMST during the last bleaching event was less than the 2 C limitation on global warming aimed at by international agreements. If global warming is restricted that limit (currently very unlikely on present policies), that means we will be getting multiple equivalent bleaching events every decade within fifty years. That is far to rapid a pace to recover from, so that bleaching events alone would be sufficient to destroy most of the Great Barrier Reef.
To repeat,
You replied as Moderator. Which facts and observations in my post are an issue?
[Rob P] This blog is based upon the findings of the peer-reviewed scientific literature and data gathered by reputable scientific organizations. Whilst it provides rebuttals to many of the common climate myths, we don't debunk every single myth some dude on the internet just came up with. If you don't accept the findings of decades of scientifc research, that's up to you, however it's not encumbent on SkS to debunk every cockamamie idea that comes along. Nor do we provide a service for spam to sites to promote the absurd. So no more links unless they are to legitimate sources (see the Comments Policy).
Casual readers, however, might be interested to see the anomalous sea surface temperatures on the Northern GBR in 2016 that caused so much coral mortality. Note the extraordinary anomalous bleaching stress (thick black line) in the bottom left-hand side of the image, as compared to the three previous (non-bleaching) years.
[Firstly to John Abraham; I should have said this earlier - I wish you well with your adoption.]
To Moderator Rob P.
The title of this article is “Climate scientists have warned us of coral bleaching for years. It’s here”
My #4, to which you seem to object, simply states
1. That it has been observed since at least 1965. (By Ron & Valerie Taylor of whom you should be well aware as you say you scuba.
2. I observe where such previous and current coral bleaching has occurred.
In other words, you don’t seem to notice I agree with you that bleaching occurs. I also agree that it will happen in future – but that it has also been observed to occur further back in time than suggested by the article.
Is it necessary for “dude” “spam” and “cockamanie”?
[Rob P] - Heat-related coral bleaching on the GBR, IIRC, goes back at least as far as the 1920's (anecdotally at least). But those were small localized events, and nothing like the large-scale bleaching events occurring today which can be many thousands of square kilometers in extent.
We cannot yet be certain, but it is unlikely that mass coral bleaching has, until very recently, occurred for thousands of years. The last major event believed to about 4000 years ago in the eastern Pacific due to, the authors claim, a more extreme ENSO cycle - see Toth et al (2012). And the last Interglacial, the Eemian, saw a global retreat of coral reefs away from the equator too (Kiessling et al [2012]).
So past and present 'observations' in the peer-reviewed scientific literature paint a consistent picture: when summer sea surface temperatures become too hot, coral bleach and often die. With a warming ocean we expect the frequency and intensity of bleaching to increase - as we are witnessing. In the not-too-distant future the tropical oceans will become too warm and coral reefs will be destroyed - as has happened in the past many times when things got too hot for them.
Of course this doesn't have to be, but humans, collectively, have shown no intention of curbing industrial carbon emissions and so the demise of coral reefs seems inevitable.
To Rob P.
Thank you.
1. Rob P’s quote “We cannot yet be certain, but it is unlikely that mass coral bleaching has, until very recently, occurred for thousands of years.”
Aren’t Valerie Taylor’s observations large-scale? They were 50 years ago and bleaching was as extensive as today’s.
2. The corals also self-repaired later - despite CO2 levels being higher. If bleaching is caused by warming due to high CO2 levels, how is it that repair occurred at higher levels than the damage? In spite of this you conclude
“Of course this doesn't have to be, but humans, collectively, have shown no intention of curbing industrial carbon emissions and so the demise of coral reefs seems inevitable.
3. [You know where to find more on this topic.] As bleaching/repair occurs sporadically, one would suspect the cause to also be sporadic. Undersea volcanism fits the bill, both in location and in its irregularity, and it produces localised toxicity and heating; witness the Qld, etc floods in 2011 (when bleaching followed) and 2016 which match the preceding large Mag seismicity around Vanuatu. Expect more bleaching soon.
4. The Eemian was about 2C higher than now (Vostok data). As you note, such temperatures may well recur.
5. I’m still puzzled by the this article’s title when the Taylors - and you - note that bleaching has preceded the “warnings” by decades.
[Rob P] - "Aren’t Valerie Taylor’s observations large-scale?"
And yet no film footage. Curious considering the amount of underwater filming that they have captured over the decades.
pjcarson2015 @9:
1)
That is not what Valerie Taylor said. She said that "In 1965 we went from one end of the reef to the other, over six months, and we found bleaching then." The phrase "we went from one end of the reef to the other" refers to the extent of the travel. It does not indicate the extent of the bleaching, which from what Valerie Taylor said, may only have been at a few locations on the reef.
More importantly, the 1965 bleaching virtually escapes comment either in scientific publications, or on the web (not to mention from Valerie Taylor's films). While the 2016 event was comparable to that of 1998 and 2002, 1965 certainly was not.
2) In the 1998 and 2002 events, 50% of effected reefs were bleeched, and there was lasting damage to 5% of reefs. In other words, reefs can, but do not always recover from bleeching events, and the more intense the event the less likely is recovery.
3) First, bleaching events are not sporadic. They were virtually unheard of prior to the 1980s, when they became common. Undersea volcanic activity did not spike at that time, but sea temperatures did, and high sea temperatures are highly correlated with bleaching events.
1. Rob P: Are you doubting Valerie’s honesty? (Be careful in a public forum.) Are you sure there’s no footage? There are probably some around still. I remember seeing bleaching on film from about that time – probably the Taylors’, perhaps Cousteau’s – but such events were then seen as another unexplained natural phenomenon about which people weren’t jumping up and down. (Note Tom Curtis re 1965.)
2. #10 Tom Curtis.
As I quoted in #3, “I’ve seen reefs in PNG that were as white as snow …”
indicates large scale – yet they recovered. Don’t be so selective in what you read.
If high CO2 and temperatures caused these in 1965 (or even back to the 1920s according to Rob P), then how did they recover in higher CO2 (and therefore higher temperatures according to AGW)? Why do reefs bleach sporadically then recover?
[“Sporadic” = occurring at irregular intervals or only in a few places.]
Underwater observations of any sort were scarce before Cousteau’s innovations in the 1940s. The Taylors were among the pioneers of underwater documentaries, starting ca 1965. One can’t see bleaching if one’s not there, but the Taylors certainly saw extensive bleaching before the 1980s.
3. Your statement “Undersea volcanic activity did not spike at that time, but sea temperatures did, and high sea temperatures are highly correlated with bleaching events.”
You’ve no idea if that’s correct. Undersea volcanic activity has simply not even been observed let alone recorded until the past 10 (or less?) years. Even Black Smokers were first observed in the mid 1970s. They were a surprise that helped substantiate Wegener’s theory.
4. Which high sea temperatures are you referring to, general or localised? It’s difficult to assign CO2 as the cause unless it’s general. The thermal stress graph in Rob P’s response to my #3 shows it is localised, albeit carried on ocean currents. Undersea volcanic activity produces toxins plus heat from magma, satisfying those criteria easily. Chapters 2 & 4 show it also matches the timing criteria.
[Rob P] If you have links to Taylor's film footage of GBR coral bleaching in 1965 then please share. If no footage exists, and given the lack of scientific evidence, such claims can be summarily dismissed.
pjcarson2015 - It's all about numbers and trends, and singleton videos are in effect only anecdotal evidence without the numbers. The comprehensive numbers and trends from both periods indicate that current changes are, indeed, unlike those of the 1960's.
[Rob P] - Indeed. In March 2016, sea surface temperatures on the Great Barrier Reef were much warmer than March 1965. So we'd expect largescale coral bleaching in 2016, but not 1965.
Incidentally, although difficult to localize, undersea volcanoes are well accounted for in total volume, by examining airborne CO2 isotopic fractions. Your imagined volcanic influences simply don't exist, not in any proportion or time sequence that would support your arguments.
KR #12: Comprehensive numbers and trends for pre and post 1960s, please show them!
Do you also doubt Taylors' observations? Eyesight and film is better than model numbers.
Do you have ANY data to show that current changes are different? Absence of data arising because no-one was looking does not count.
#13: How does examining AIRborne CO2 give you evidence of UNDERsea volcanoes!! They don’t produce airborne CO2 – unless from shallow seeps, they are generally kms below surface and CO2 dissolves. I mentioned an example in #3 and #9, and the large storms on the eastern coast over the past weeks are further examples. (Large Mag around Vanuatu again.)
It now turns out that pjcarson2015 @11 (third point) now wants us to believe that:
i) Undersea volcanoes change ocean chemistry in their region so little as to be undetectable except over the last ten odd years;
ii) But that they change the ocean chemistry so much thousands of miles downstream that they cause mass bleachings; and that
iii) Undersea volcanoes have been undetectable except in the last ten years;
iv) But that he has been able to establish a clear correlation between such eruptions and bleaching events going back over decades;
v) And the established connection between bleaching events and high SST going back over four five decades swhould be ignored based on his evidence, which by his own claim cannot cover more than a decade or so.
He also wants us to believe that mass coral mortalities have been detectable going back to the 1870s (see graph @5 reproduced below), and major Crown of Thorns Starfish (Acanthaster) outbreaks have been detectable since the 1900s, while mass coral bleachings cannot possibly have been detected prior to the 1960s. Indeed, given the rapid ramp up of mass coral bleachings in the 1980s, he really requires us to believe they were not significantly detectable until the 1980s, for if he does not he must accept that they have recently become more frequent with the rise in SST.
In my opinion, he has already qualified to dine at Milliways, and should give it a rest.
oderator’s response to KR.
“So we'd expect largescale coral bleaching in 2016 but not 1965. “
Just as I wrote and explained for 2016 in #9 point 3.
How do YOU explain the warm peaks in your presented graph?
Are you still not accepting pre 1965 bleaching? (It was observed in 1965, therefore it happened pre-1965 – which matches your graph’s temperature peak.)
Yet you do accept it in the 1920s!?
[BTW. The Taylors were among the first “environmental warriors”, fighting to protect sharks, etc and the GBR. Yet you doubt her observations!]
[Rob P] - The March sea surface temperature (SST) anomaly on the GBR in 1965 was 0.61°C below the 1961-1990 mean, whereas the March 2016 SST anomaly was 1.33°C above the mean. March 1965 ranks as the 20th coolest year in the entire record. Coral would not have been bleaching in 1965 because SST's were too warm.
And the large year-to-year fluctuations in sea surface temperature on the GBR, despite a long-term warming trend, are largely due to ENSO. In the 2nd year of an El Nino event, anomalously warm surface water entrained in the surface circulation is transported to the Coral Sea via the South Equatorial Current - the westward flowing current which is the northern arm of the anti-clockwise rotating South Pacific subtropical gyre. The anomalous warmth raises the summertime SST above normal - which is why the peaks in the graph tend to occur in El Nino years.
What is doubted, it not what Valerie said, but your understanding of what she observed. I havent found the data sources of her observations for evaluation but I did find this from Ove Hoegh-Guldberg in which her observations are put in context:
"Underwater film makers like Valerie Taylor (personal communication) who extensively filmed on the Great of Barrier Reef during the 1960s and 1970s never saw coral bleaching on the scale seen since 1979. "
Comparisons with times of past high temperature have to be considered against the rate of warming which is far faster then any previous occurance except maybe PETM when nearly lost corals altogether.
And frankly, I have far more faith in systematic surveys than in one persons observations.
#17 scaddenp.
1. I quoted Valerie in #3. What have I misunderstood?
2. Ove was about 7 years old in 1965, and completed his PhD in 1982; how could he compare relative bleaching if he hadn’t seen past bleaching? (See 5 below).
3. Wasn’t Ove the one appearing on Sir David Attenborough’s program “Death of the Oceans” the effects of higher CO2 levels on pH by blowing his own breath (ca 5% CO2) into seawater? A tad unrealistic - deceptive even?
4. I actually had a “conversation” with Ove (after one of his radio presentation) via a Bulletin Board concerning reef problems – it was dial-up then! - about 20 years ago. I asked him if they tested for H2S. Nope. They’re unlikely to find something if they don’t test for it!
5. One person’s observations are on TV for all to see. I’ve seen it.
So, either Ove has seen it – proving Taylors’ vision exists/existed- or he hasn’t - and his statement is false.
You choose which.
6. Until AGW raised its head ca 1985, not much concern was raised about bleaching, and was reflected in when or if it was reported.
pjcarson2015
If it is H2S from volcanoes, presumably you can point to evidence along the current pathways from them to the GBR where we can see elemental Sulphur deposited on the sea floor as a result of H2S reacting with dissolved Oxygen and precipitating out. Whereas in contrast, when major H2S events have occurred in the geological record they come about at times of depleted oxygen in the oceans and large scale anaerobic bacteria population explosions
1/ it is your framing i am objecting to. Your inference doesnt go with the other quote does it? Tom here pointed out that you were inferring more from her statement than it allowed.
2/ I have no idea who Ove is apart from fact that he is professional scientist studying coral. Comments about him or his age sound like rhetori to me.
5/ Sorry, on one TV show you cannot show pictures that give any framework to how widespread an event is, nor its context in larger time frame.
Was there a coral bleaching event in 1965? yes. Is it comparable to events today in severity and coverage?- you need the larger scale evidence. Valerie says no but you appear to not to like that statement, but project heaps from the other one. Drawing a long bow from one observation instead of decades of study is highly unconvincing to me.
scaddenp @20, I think you will find that Ove is Australian Research Concil Laureate Fellow, Professor Ove Hoegh-Guldberg. His also John Cook's boss, and author of a very relevant series of posts on SkS (Part 1, Part 2, Part 3). I am unsure on what basis PJ Carson claims to be on a first name basis with him (his only described interaction certainly does not cut it).
scaddenp @20:
As previously noted, Valerie Taylor only state the extent of her, and her husbands travels in 1965, not the extent of the bleaching. However, she does not state that the bleaching was limited. From the information she gives alone, it could have been one or two small patches of bleaching, or a bleaching event comparable to that in 1998 and 2016. Of course, we know on other grounds that the later is not the case. Further, she does not even state when the bleaching occurred, or its cause. The bleached areas they saw could have been remnants of a bleaching event in the previous two years. The bleaching could also have been caused by large inflows of fresh water (as happens on inshore reefs during floods). It may have even be a Crown of Thorns Starfish outbreak, whose initial impact of the reef is superficially similar.
Not only is her account vague, but it is also that of a non-expert. She is a very experienced diver, but so also is Ove Hoegh-Guldberg, who was collecting for an Oceanarium before he left high school, and has been diving for at least 39 years. What Ove Hoegh-Guldberg adds to that is a lifetime of intensive research which makes him an expert, something pjcarson would immediately acknowledg, if only Ove Hoegh-Guldberg agreed with him. Unfortunately he does not, so he has to talk up a non-expert who does not explicitly disagree rather than acknowledge genuine expertise.
pjcarson2015 @20:
You assert:
6. Until AGW raised its head ca 1985, not much concern was raised about bleaching, and was reflected in when or if it was reported.
How do you know this to be true?
#23 John Hartz. “How do you know this to be true? “
Because I’m old enough for my observations to be contemporaneous.
Do you have evidence to the contrary?
John Hartz @23, I was expecting a bullshit answer from pjcarson2015, and you got it.
We can check his hypothesis independently, however. Suppose a low level concern for reef health as a background. Then prior to the massive increase in interest in global warming circa 1990, mentions of "Crown of Thorns Starfish", and "Coral bleaching" should follow similar patterns prior to 1990s, after which interest in coral bleaching should take of. In contrast, if coral bleaching was virtually unknown before the 1980s, there should be little mention of coral bleaching prior to then, and then mentions should rise with the rise in coral bleaching events. Looking at an n-gram search of the two terms, however, we find a rise in interest in COTS in the 1970s that was not matched by a similar rise interest in coral bleaching, as would have been the case had bleaching events been a regular occurence and the concern only be with reef health. Following the global bleaching event in 1983, and especially that of 1998, there is a rapid rise in interest in coral bleaching, which fell significantly a few years after the 2003 bleaching event.
That is, the documentary evidence strongly favours the rise in bleaching events resulting from a rise in SST as the cause of the interest in bleaching events.
Of course, if that is not evidence enough, I also am old enough for my observations to be contemporaneous; and my observations are incompatible with pjcarson2015's thesis. Of course, such anecdotal claims are irrelevant as evidence, in either direction - but Carson cannot count his observations as evidence while excluding mine with out transparent special pleading.
Tom Curtis. I haven’t bothered to answer your #25 #5, etc, because of your lack of respect. (It won’t help your comprehension but try using a spell-checker.)
pjcarson2015 @26, a person who assumes scientists are uninformed buffoons as you do deserves no respect. Especially when you do so on the basis of such transparently inadequate arguments.
pjcarson2015:
You asserted:
I asked:
You responded:
Can you document evidence that your memory is accurate?
What do you mean by the phrase, Until AGW raised its head ca 1985 ?
Does your initial assertion apply globally, or just to Australia?
#28 John Hartz: The IPCC was started in 1988. I think concerns about bleaching emerged rather later than those about CC. That places bleaching concerns mid-1980s at earliest. Anyway, far later than 1965.